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Chronic sleep loss is hard to overcome

Even a good night's sleep doesn't totally compensate for many weeks of sleep loss, according to a new study. And it's the late-night period when the accumulation of sleep loss may be most apparent.

Researchers at Brigham and Women's Hospital examined the effect of weeks of insufficient sleep on performance. They scheduled nine healthy volunteers to live for three weeks on a schedule consisting of 43-hour periods in which they were awake for 33 of those hours. That equals about 5.6 hours sleep for every 24 hours. They looked at how the volunteers performed on cognitive reaction tasks from chronic sleep loss and disrupted circadian rhythms.

The study showed that after waking from a 10-hour sleep, the subjects' performance was good, but it deteriorated as each 33-hour waking period went on. Indeed, an individual with chronic sleep loss who worked extended hours into the night can have reaction times about 10 times slower than normal, increasing the risk of accidents and mistakes.

The study also found that when the body's circadian rhythms were at their lowest (late night and early morning) reaction times were slower, especially with chronic sleep loss. During high-performing periods of the circadian rhythm (late afternoon and early evening) reaction times were normal despite chronic sleep debt. The study is published in the journal Science Translational Medicine.

"Many people have a false sense of reassurance that they can quickly recover from a chronic sleep debt with just one or two days of good sleep," the lead author of the study, Daniel Cohen, said in a news release. ". . .However, the lingering effect of chronic sleep loss causes performance to deteriorate dramatically when these individuals stay awake for an extended period of time, for example, when they try to pull an 'all-nighter.' "

The study is further evidence that people who work irregular shifts or night shifts face a real hurdle in trying to perform their jobs safely and productively.